attoissue.hs

{-# LANGUAGE OverloadedStrings #-}

import              Data.Attoparsec.Text
import              Data.Text (Text)
import qualified    Data.Text as T
import              Prelude   hiding (take)

input :: Text
input = "𝟘a"

-- homemade takeTill
takeTill' :: (Char -> Bool) -> Parser Text
takeTill' f = do
    result <- peekChar
    case result of
        Just ch -> do
            if f ch
                then return T.empty
                else do
                    ch' <- take 1
                    rest <- takeTill' f
                    return (ch' `T.append` rest)
        Nothing  -> return T.empty

main :: IO ()
main = do
    putStrLn "== input string =="
    print input
    
    putStrLn "== takeTill =="
    parseTest (takeTill ((==) 'a')) input >>= print

    putStrLn "== takeTill' (homemade) =="
    parseTest (takeTill' ((==) 'a')) input >>= print

result.md

== input string ==
"\120792a"
== takeTill ==
Done "\57304a" "\120792"
()
== takeTill' (homemade) ==
Done "a" "\120792"
()